Most useful at least one month after a suspected drug exposure or for chronic drug exposures

Oral fluid

Useful for detection of free drug

Represents a time frame of drug use or exposure most similar to serum/plasma

Testing approach

Drug testing may be performed based on a targeted analysis of one or more drug classes, as in the case of therapeutic drug monitoring or confirmatory testing, or based on a qualitative screen that identifies several drug classes

Drug screens can be ordered as “screen only” or with reflex to confirmation

Any drug class identified in the screen would be confirmed by a targeted assay

Targeted screening and comprehensive screening tests covering a range of drug classes are available

Meconium testing is not available as “screen only” due to the high rate of false positive results for some analytes

Testing to support a wide variety of therapeutic drugs (eg, anticonvulsants, antidepressants, antipsychotics, antiarrhythmics, immunosuppressants) is available; more details are available from the laboratory performing the test

Purpose

Compare values at steady-state to published therapeutic targets/ranges or individual patient history to optimize dose

Examples of drugs for which therapeutic drug monitoring is observed – anti-epileptics, immunosuppressants, anti-arrhythmics, and antibiotics

Evaluate clinical signs and symptoms, failure to respond, and toxicity, particularly for drugs with a narrow therapeutic index

Specific drug test performed after a drug screen to confirm the identity of a drug class, individual parent drug, and/or drug metabolite; confirmatory tests are frequently based on mass spectrometric methods and are often quantitative.

Cutoff

Threshold concentration for a drug class, specific drug, or drug metabolite above which a specimen is reported as “positive” or “present”; cutoff may be defined by the manufacturer of a commercial kit (eg, immunoassay) or based on the limit of quantitation validated for a laboratory-developed test (eg, mass spectrometry).

Drug screen

Test intended to identify the presence or absence of one or more drug classes or specific drugs.

Free drug

Drug or drug metabolite not bound to protein or other moieties such as glucuronides; biological activity, transport, and elimination of drugs and drug metabolites is often different for a free versus a bound drug.

Forensic

Relating to or dealing with evidence intended for use in a court of law (eg, to support crime and death investigations, workers’ compensation claims, and pre-employment testing).

Hydrolysis

Chemical process of decomposition involving the splitting of a bond and the addition of the hydrogen cation and the hydroxide anion of water.

Common laboratory technique used to dissociate glucuronide and other conjugates of drugs in order to improve detection of many drugs in urine.

Methods that employ hydrolysis prior to analysis are presumed to generate a “total” drug concentration.

Limit of detection (LOD)

Concentration at which the target compound can be identified.

Limit of quantification (LOQ)

Concentration at which quantitative results can be reported with a high degree of confidence.

Metabolite

Any product of metabolism; metabolites can be pharmacologically or toxicologically active or inactive.

Pharmacodynamics

Study of drug response, particularly the mechanisms associated with the binding and interactions of pharmacologically active molecules at their tissue site(s) of action.